Heat-resisting alloy and structure



PATENT OFFICE.

NOAK VICTOR EYBINETTE, OF WILMINGTON, DELAWARE.

HELT-BESISTING ALLOY AND STRUCTURE.

No Drawing.

' er or less extent by the deoxidizing action rigid, even under a heavy which they exert. Such alloys are suited for wire, sheets, and ordinary castings such as heat treating containers, etc.

There exists, however, a demand for heat enduring metallic structures which have the peculiar property of being extraordinarily oad, at temperatures ranging from around 1500 to around 2000 F. The present invention is designed to fill such a demand. The invention is also designed to fill the demand for less rigid structures possessing some machinability.

I have discovered that a comparatively large amount of carbon, together with a small amount of aluminum will make low percentage chrome-nickel iron alloys heat enduring; such alloys being below the limits of heat resistance without such addition of carbon and aluminum. This discovery allows me to produce heat enduring alloys of novel composition and with novel properties. The new alloys of the present invention contain the following ingredients in approximately the following proportions:

Nickel from about 5 to about 10%. Chromium from about 15 to about 25%. Carbon from about 1 to about 2%. Aluminum from about to about 2%. The remainder mainly iron.

' Such alloys, without the carbon and aluminum in amounts such as indicated, would not be particularly heat resisting; but when carbon and aluminum are both present in proper amount, and when the other in edients are properly proportioned, the al oy is not only heat resisting but structures made therefrom have the valuable property of rigidity under a heavy load at high temperatures.

The aluminum content of the alloy can Application filed February 5 192,4. Serial Io. 690,800.

be increased several percent, but such increase does not correspondingly increase the strength, and may cause trouble in casting, and, in general, the aluminum should not be increased materially above the amounts indicated. A lowering of the carbon content below the approximate limit indicated causes a considera le lowering in the stiffness of the castings. The lowering of the nickel content tends to cause brittleness at ordina temperatures while the increase of the nickel content tends to cause toughness and ductility instead of rigid stifl'ness. At about 10% nickel, the alloy possesses some machinabil ity, e. g. with an emery wheel or chipping tool. Higher proportions of nickel do not produce correspondingly better qualities. A higher percentage of carbon increases machinability. Carbon below 1% or over 2% decreases heat endurance and strength. At 2% carbon and 10% nickel the alloy still has high heat endurance and fair strength, but the extreme rigidity or high elastic limi and high modulus of elasticity are sacrifice for a fair degree of machinability. Such alloy is suitable for heat treatment containers, etc.

For highest strength 6-7% nickel and 1 70 carbon and aluminum are recommended. Chromium should be held at 18- 20%. Lower chromium decreases both heat endurance and strength. Higher chromium gives no corresponding benefit. The silicon content does not appear to be of particular importance so long as the silicon is below about 1%, e. g. around 0.75%, and the amounts of sillcon commonly found in the iron from which the allo is made will or dinarily be such that it oes not require to be increased or decreased in amount. Manganese may be present in small amount but if present in too large an amount it has a toughening effect and tends to decrease or destroy the desired rigidity and stiffness. When increased nickel is used in the alloy, an increased amount of aluminum will ordinaril be required, but since a high content 0 aluminum tends to interfere with casting in sand molds, the nickel and aluminum contents should for best results be kept sufiiciently low to avoid such interference.

I have found that a particularly advantageous composition of the alloy for making castings which are rigid at high temperatures is about 20% chromium, about 7% nickel, about 1% aluminum, about 1 carbon, up to about 1% silicon, up to about Ill) manganese and the remainder mainly iron. Castings made of this alloy are so hard at ordinary tem eratures that they can be worked only wit great difficulty with an emery wheel. It is also practically impossible to cut such an alloy with a welding torch. It is therefore unusually well suited for use in safes and similar uses as well as for heat enduring structures.

Such an alloy at a temperature of about 1500 F. has been found to have an elastic limit of about 8,000, a tensile strength of about 35,000, and a modulus of an elasticity of about 9,000,000. So far as I am aware no other commercially known alloy has such properties.

The alloy is of more or less general use where heat enduring alloys are desired and particularly where castings are desired which have great rigidity under a heavy load at high temperatures. It is not so well adapted, on account of its great hardness for use in certain hi h tem erature The new alloys are relatively inexpensive to manufacture because of their low nickel content, but they nevertheless ossess particularl valuable properties of t e character referre to.

I believe that I am the first to discover that an alloy of the contents hereinbefore specified of chromium and nickel, which otherwise would not be heat resisting to any practical extent, can be made so by adding a considerable amount of carbon and aluminum at the same time. I also believe that I am the first to discover that such an alloy is particularl suitable for structures where rigidness un er a heavy load is wanted at high temperatures.

It will be' evident that small additions of many other metals and substances can be added to the alloy without materially changing the properties thereof, and in some cases with an improvement in the desirable pro erties of the alloy and of the structures ma e therefrom.

The new alloys and castings can be produced at a moderate expense, permitting them to be used commercially in large installations .where rigidity at high temperatures is desired.

I claim:

1. An alloy which is heat resisting at high temperatures containing the following ingredients in ap roximately the following proportions: nic el from about to about 10%, chromium from about to about carbon fromabout 1 to about 2%, aluminum from about to about 2%, the remainder mainl iron.

2. alloy which is heat resisting at high temperatures containing the following ingredients in approximately the following proportions: chromium about 18 to 20%, n'ckel about 6 to 7%, aluminum about to 1%, carbon about 1 the remainder mainly iron.

3. An alloy having approximatel the following com osition:-about 20% c iromium, about 7% nickel, about 1% aluminum, about 1 5% carbon, and the remainder mainly iron, said alloy having approximately the following properties at a temperature of about 1500 F. namely, an elastic limit of about-8,000, a tensile strength of about 35,- 000 and a modulus of elasticity of about 9,000,000.

4. A cast structure made of an alloy of the composition specified in claim 1.

5. A cast structure made of an alloy of the composition specified in claim 2, said cast structure possessing great rigidness under a heavy load at temperatures ranging from about 1500 to about 2000 F.

6. Cast I-beams and other structural shapes made of an alloy such as specified in claim 1, said cast structures being characterized by great rigidity at high temperatures. I

7. Cast I-beams and other structural shapes made of an alloy such as specified in claim 2, said cast structures being characterized by great rigidity athigh temperatures.

In testimorlig whereof I aifix m si NOA VICTOR HYBIlIE ature. I TE. 

